Field of the Invention
The present invention relates generally to an improved internal combustion (IC) power plant of the four-stroke, or four-cycle type. Four-stroke engines inherently have a pulsatile intake and exhaust flow, into and from the combustion chamber(s). The inventive IC power plant has an enhanced or improved pulsatile exhaust gas flow so that one or more advantages, such as: improved volumetric efficiency, improved fuel economy, improved torque and horsepower production (especially at low engine speeds), reduced catalytic converter size (i.e., for gasoline-fueled automotive engines), as well as other benefits are realized.
Related Technology
IC engines generally and historically have used one or more mufflers in order to both reduce the noise level of the engine exhaust and possibly to enhance pleasant frequencies or tones in the exhaust. The conventional mufflers and exhaust systems are also configured to control undesired resonance(s) or droning in the exhaust system, and to provide a desired level of quietness, or in some cases to provide a somewhat more noisy “performance” sound for an automobile for example. In the automotive context, exhaust systems are generally graded or ranked in comparison to the performance loss that they cause in comparison to an “open pipes” exhaust system, and in terms of the level of exhaust noise they inflict on passengers and on bystanders of the vehicle.
For some time intake and exhaust systems for IC engines (i.e., in passenger automobiles especially) have been known which include resonant or reactive chambers intended to reduce resonance or droning of the intake or exhaust system at particular engine speeds, or within particular engine speed ranges, so that passengers of the vehicle are not subjected to an undesirable noise, vibration, or harshness (i.e., “NVH” in common engineering terminology). These known resonant chambers for abatement of NVH are generally added to a vehicle solely in the interest of comfort and civility of the vehicle. A well-known example of the use of a resonant chamber to address a noise, vibration, or harshness (NVH) problem is presented in US patent publication No. 2006/000067 A1, dated 5 Jan. 2006, by Dale F. Osterkamp, et al. The Osterkamp publication is believed to disclose a sound dampening assembly, including a resonant chamber connected at a determined location along the length of an automotive exhaust system at an identified pressure anti-node (not at a velocity node) of the objectionable vibration (i.e., sound) it is wished to alleviate or eliminate. This anti-node is located by identifying the location along the length of the exhaust system where the objection vibration is most pronounced. No improvement in engine performance (i.e., torque or horse power output) or fuel economy is known to result from such a resonant chamber used to control NVH.